Hopefully this one doesn’t kill herself like an earlier mistress did.

This former A list mostly television actor who walked away from a hit show which is still on the air several years later is cheating on his long suffering wife again. Hopefully this one doesn't kill herself like an earlier mistress did.

McDreamy’s legacy turned into a nightmare when he was suddenly fired from Grey’s Anatomy last month. But RadarOnline.com has learned that trouble was brewing on set for months — all over Dempsey’s relationship with a much-younger Grey’s staffer!

According to a show source, “Patrick’s affair with the staffer Opens a New Window. on the show began last August.”

“It was obvious to everyone Patrick was [sleeping with] her,” the insider told Radar. “It got very messy and emotional on set and became a huge liability.”

“Patrick would remain in his trailer after hooking up with her on set and refuse to come out,” the source claimed. “He had also been complaining about the storyline of his character, and felt he wasn’t getting enough screen time.”

Amid the drama, Dempsey was “suspended” for a while, according to the source, and the female staffer was allegedly moved off set to Rhimes’ production offices.

“Shonda doesn’t put up with any off-screen antics,” said the source.

Dempsey was soon allowed to come back, but the damage had already been done.

“There were lingering feelings of anger towards Patrick, and it was only getting worse,” the source said. “This is when he began showing up late, not remembering lines. Shonda had no other choice but to fire him.” – Source